[S390] vmur: Use wait queue instead of mutex to serialize open
If user space opens a unit record device node then vmur is leaving the kernel
with lock open_mutex still held to prevent other processes from opening the
device simultaneously. This causes lockdep to complain about a lock held when
returning to user space.
Now the mutex is replaced by a wait queue to serialize device open.
Signed-off-by: Frank Munzert <munzert@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
diff --git a/drivers/s390/char/vmur.c b/drivers/s390/char/vmur.c
index 7689b50..83ae9a8 100644
--- a/drivers/s390/char/vmur.c
+++ b/drivers/s390/char/vmur.c
@@ -100,7 +100,8 @@
urd->reclen = cdev->id.driver_info;
ccw_device_get_id(cdev, &urd->dev_id);
mutex_init(&urd->io_mutex);
- mutex_init(&urd->open_mutex);
+ init_waitqueue_head(&urd->wait);
+ spin_lock_init(&urd->open_lock);
atomic_set(&urd->ref_count, 1);
urd->cdev = cdev;
get_device(&cdev->dev);
@@ -678,17 +679,21 @@
if (!urd)
return -ENXIO;
- if (file->f_flags & O_NONBLOCK) {
- if (!mutex_trylock(&urd->open_mutex)) {
+ spin_lock(&urd->open_lock);
+ while (urd->open_flag) {
+ spin_unlock(&urd->open_lock);
+ if (file->f_flags & O_NONBLOCK) {
rc = -EBUSY;
goto fail_put;
}
- } else {
- if (mutex_lock_interruptible(&urd->open_mutex)) {
+ if (wait_event_interruptible(urd->wait, urd->open_flag == 0)) {
rc = -ERESTARTSYS;
goto fail_put;
}
+ spin_lock(&urd->open_lock);
}
+ urd->open_flag++;
+ spin_unlock(&urd->open_lock);
TRACE("ur_open\n");
@@ -720,7 +725,9 @@
fail_urfile_free:
urfile_free(urf);
fail_unlock:
- mutex_unlock(&urd->open_mutex);
+ spin_lock(&urd->open_lock);
+ urd->open_flag--;
+ spin_unlock(&urd->open_lock);
fail_put:
urdev_put(urd);
return rc;
@@ -731,7 +738,10 @@
struct urfile *urf = file->private_data;
TRACE("ur_release\n");
- mutex_unlock(&urf->urd->open_mutex);
+ spin_lock(&urf->urd->open_lock);
+ urf->urd->open_flag--;
+ spin_unlock(&urf->urd->open_lock);
+ wake_up_interruptible(&urf->urd->wait);
urdev_put(urf->urd);
urfile_free(urf);
return 0;
diff --git a/drivers/s390/char/vmur.h b/drivers/s390/char/vmur.h
index fa95964..fa320ad 100644
--- a/drivers/s390/char/vmur.h
+++ b/drivers/s390/char/vmur.h
@@ -62,7 +62,6 @@
struct urdev {
struct ccw_device *cdev; /* Backpointer to ccw device */
struct mutex io_mutex; /* Serialises device IO */
- struct mutex open_mutex; /* Serialises access to device */
struct completion *io_done; /* do_ur_io waits; irq completes */
struct device *device;
struct cdev *char_device;
@@ -71,6 +70,9 @@
int class; /* VM device class */
int io_request_rc; /* return code from I/O request */
atomic_t ref_count; /* reference counter */
+ wait_queue_head_t wait; /* wait queue to serialize open */
+ int open_flag; /* "urdev is open" flag */
+ spinlock_t open_lock; /* serialize critical sections */
};
/*